It is common practice to desulphurise oil fractions with hydrotreatment units in refineries and with suitable technologies at acid natural gas extraction sites, thus producing large amounts of sulphur as a by-product, which is stored in liquid form in tanks or solidified in large blocks, pastillated or formed by a wet process into small flakes or pellets to promote heat dispersion in the solidification process and facilitate handling and transport. In this way, huge masses can accumulate at production sites, with a length and width of dozens/hundreds of meters, and heights of 10 meters or more, which involve onerous storage/destorage operations. Depending on market requirements, efficient, economical solidification, storage and destorage techniques may be required. As sulphur possesses limited heat conductivity, in industrial practice large blocks of sulphur are obtained by feeding and layering in successive thin layers juxtaposed with thicknesses not exceeding approx. 10 cm, and preferably not exceeding 5 cm, thus guaranteeing an adequate cooling time for the molten mass, in order to give it the necessary characteristics of mechanical strength. Stratification allows effective dispersion of heat from the surface exposed to air by natural convection. In the absence of said procedure, the poured material, once cooled, forms a fragile, uneven material, characterised by the presence of cavities, possibly containing liquid sulphur, which may cause injury or damage to personnel or machinery during the processing/handling stages. Solidification of the stratified sulphur requires large areas and long solidification times. To eliminate these drawbacks, techniques are employed that form the sulphur into flakes, pellets or pastilles using coolants (generally water), which are characterised by a better heat transport coefficient than air and come into direct/indirect contact with the sulphur. These methods guarantee high productivity but are complicated and onerous, involving the use of complex equipment (grilling towers, drop-forming machines and pastillators with rotary forming rollers), considerable quantities of cooling water and a large amount of skilled labour. Sulphur has been and still is one of the most widely studied elements because of its polymorphic characteristics and special features. Orthorhombic sulphur (the form which is stable under ambient conditions) was one of the first crystalline structures to be characterised by X-rays; since then, over 50 allotropic forms of sulphur have been described, comprising structures mainly based on cyclical molecules or polymer chains. The orthorhombic structure, more commonly known as alpha-sulphur, has a characteristic pale yellow colour, is opaque and fragile, and is stable under approx. 95° C. (369° K). At higher temperatures, alpha-sulphur is transformed into the monoclinic allotrope beta-sulphur, which is stable up to melting point, at approx. 115° C. (388° K). The crystals are needle-shaped, waxy and fragile, and have an orange-yellow colour with pearly reflexes. The transformation between the two forms is reversible. Both orthorhombic alpha-sulphur and monoclinic beta-sulphur are based on molecular unit S8. The density of the two allotropes is 2.066 g/cm3 for alpha-sulphur and 2.008 g/cm3 for beta-sulphur. In the amorphous form, obtained by rapid cooling of molten sulphur, there are no crystals; in this state sulphur is hard, dark brown and elastic and is unstable, slowly transforming to crystalline rhombic sulphur; X-ray crystallography shows that this amorphous form may have a helical shape with 8 atoms. Liquid sulphur is characterised by unique physical properties; at all temperatures it contains rings having from 6 to at least 35 atoms, with S8 constituting the majority of the species together with polymeric sulphur S1, which only becomes the majority at temperatures exceeding 170° C. (443° K). Liquid sulphur is characterised by a honey-yellow colour near melting point; said colour changes reversibly, as the temperature increases, to bright yellow, then orange, then dark red, and finally red-brown close to boiling point at 445° C. (718° K). The density of liquid sulphur (at ambient pressure) declines as the temperature increases from 1,802 g/cm3 to 120° C. (393° K) to 1.573 g/cm3 at 440° C. (713° K). Sulphur has excellent heat insulating properties; its thermal conductivity declines as the temperature increases. For temperatures below 95.4° C. (368° K), the conductivity of alpha-sulphur can be approximately expressed by the law k=0.8935−3.3347×T/103+4.1524×T^2/106 (W/mK), where parameter T temperature is expressed in degrees Kelvin, ie. approx. 0.266 W/mK at approx. 27° C. (300° K), while as soon as the temperature of transition to monoclinic sulphur is exceeded, the thermal conductivity of beta-sulphur falls to approx. 0.156 W/mK. The dynamic viscosity of the molten sulphur has a minimum value of 0.007 s Pa (0.07 Poise) at approx. 157° C. (430° K), but increases by over four orders of magnitude in the low temperature range of 155-190° C. (428-463° K), reaching the maximum viscosity of 93.2 sPa at approx. 187° C. (460° K), after which the viscosity again falls to 0.1 sPa at boiling point. FIG. 1 shows the simplified phase diagram for sulphur, illustrating the solidification process at 1 atmosphere when sulphur passes from the liquid state (A) to the monoclinic beta solid state (B) to the orthorhombic alpha solid state (C). Said transformation involves a reduction in volume, which can induce a state of tension in the solidified sulphur, leading to rupture and disintegration following heat cycles or other instabilities. To solve said problem, Ducker chemically modified sulphur by adding olefins to delay its tendency to reduce in density, and to improve its mechanical characteristics. In the subsequent years, with a view to obtaining materials for industry based on sulphur and sulphur cements, the use of additives designed to chemically modify the properties of sulphur was consolidated, one example being plasticising polymers designed to induce the formation of polysulphides and alter the crystallisation of sulphur. As an alternative to the chemical approach, a solely physical approach to the problem has also been employed, using aggregates and fillers with suitable particular-size distributions as additives to control crystallisation and reduce the tensions in the solidified sulphur. Said additives with physical interaction produce a dense network of nucleation points in the molten sulphur where the crystals can grow in an orderly way, thus obtaining a compact structure with small crystals. Said methods are effective, but involve the use of large quantities of organic and/or inorganic additives, and do not produce crystalline structures of orthorhombic alpha-sulphur with high purity.